CVE-2026-27456
published 2026-04-03CVE-2026-27456: util-linux is a random collection of Linux utilities. Prior to version 2.41.4, a TOCTOU (Time-of-Check-Time-of-Use) vulnerability has been identified in the…
PriorityP424medium4.7CVSS 3.1
AVLACHPRLUINSUCHINAN
EPSS
0.12%
2.0th percentile
util-linux is a random collection of Linux utilities. Prior to version 2.41.4, a TOCTOU (Time-of-Check-Time-of-Use) vulnerability has been identified in the SUID binary /usr/bin/mount from util-linux. The mount binary, when setting up loop devices, validates the source file path with user privileges via fork() + setuid() + realpath(), but subsequently re-canonicalizes and opens it with root privileges (euid=0) without verifying that the path has not been replaced between both operations. Neither O_NOFOLLOW, nor inode comparison, nor post-open fstat() are employed. This allows a local unprivileged user to replace the source file with a symlink pointing to any root-owned file or device during the race window, causing the SUID binary to open and mount it as root. Exploitation requires an /etc/fstab entry with user,loop options whose path points to a directory where the attacker has write permission, and that /usr/bin/mount has the SUID bit set (the default configuration on virtually all Linux distributions). The impact is unauthorized read access to root-protected files and block devices, including backup images, disk volumes, and any file containing a valid filesystem. This issue has been patched in version 2.41.4.
Affected
5 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| debian | util-linux | < util-linux 2.42-1 (sid) | util-linux 2.42-1 (sid) |
| kernel | util-linux | < 2.41.4 | 2.41.4 |
| msrc | azl3_util-linux_2.40.2-3_on_azure_linux_3.0 | — | — |
| msrc | cbl2_util-linux_2.37.4-10_on_cbl_mariner_2.0 | — | — |
| util-linux | util-linux | < 2.41.4 | 2.41.4 |
CVSS provenance
nvdv3.14.7MEDIUMCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N
osv4.7MEDIUM
vendor_debian4.7MEDIUM
vendor_msrc4.7MEDIUM
vendor_redhat4.7MEDIUM
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Red Hat
util-linux: TOCTOU in the mount program when setting up loop devices
vendor_redhat·2026-04-03·CVSS 4.7
CVE-2026-27456 [MEDIUM] CWE-367 util-linux: TOCTOU in the mount program when setting up loop devices
util-linux: TOCTOU in the mount program when setting up loop devices
util-linux is a random collection of Linux utilities. Prior to version 2.41.4, a TOCTOU (Time-of-Check-Time-of-Use) vulnerability has been identified in the SUID binary /usr/bin/mount from util-linux. The mount binary, when setting up loop devices, validates the source file path with user privileges via fork() + setuid() + realpath(), but subsequently re-canonicalizes and opens it with root privileges (euid=0) without verifying that the path has not been replaced between both operations. Neither O_NOFOLLOW, nor inode comparison, nor post-open fstat() are employed. This allows a local unprivileged user to replace the source file with a symlink pointing to any root-owned file or device during the race window, causing the S
Microsoft
util-linux: TOCTOU Race Condition in util-linux mount(8) - Loop Device Setup
vendor_msrc·2026-04-02·CVSS 4.7
CVE-2026-27456 [MEDIUM] CWE-59 util-linux: TOCTOU Race Condition in util-linux mount(8) - Loop Device Setup
util-linux: TOCTOU Race Condition in util-linux mount(8) - Loop Device Setup
Mariner: Mariner
GitHub_M: GitHub_M
Customer Action Required: Yes
Debian
CVE-2026-27456: util-linux - util-linux is a random collection of Linux utilities. Prior to version 2.41.4, a...
vendor_debian·2026·CVSS 4.7
CVE-2026-27456 [MEDIUM] CVE-2026-27456: util-linux - util-linux is a random collection of Linux utilities. Prior to version 2.41.4, a...
util-linux is a random collection of Linux utilities. Prior to version 2.41.4, a TOCTOU (Time-of-Check-Time-of-Use) vulnerability has been identified in the SUID binary /usr/bin/mount from util-linux. The mount binary, when setting up loop devices, validates the source file path with user privileges via fork() + setuid() + realpath(), but subsequently re-canonicalizes and opens it with root privileges (euid=0) without verifying that the path has not been replaced between both operations. Neither O_NOFOLLOW, nor inode comparison, nor post-open fstat() are employed. This allows a local unprivileged user to replace the source file with a symlink pointing to any root-owned file or device during the race window, causing the SUID binary to open and mount it as root. Exploitation requires an /etc
OSV
CVE-2026-27456: util-linux is a random collection of Linux utilities
osv·2026-04-03·CVSS 4.7
CVE-2026-27456 [MEDIUM] CVE-2026-27456: util-linux is a random collection of Linux utilities
util-linux is a random collection of Linux utilities. Prior to version 2.41.4, a TOCTOU (Time-of-Check-Time-of-Use) vulnerability has been identified in the SUID binary /usr/bin/mount from util-linux. The mount binary, when setting up loop devices, validates the source file path with user privileges via fork() + setuid() + realpath(), but subsequently re-canonicalizes and opens it with root privileges (euid=0) without verifying that the path has not been replaced between both operations. Neither O_NOFOLLOW, nor inode comparison, nor post-open fstat() are employed. This allows a local unprivileged user to replace the source file with a symlink pointing to any root-owned file or device during the race window, causing the SUID binary to open and mount it as root. Exploitation requires an /etc
OSV
CVE-2026-27456: [util-linux: mount(8) TOCTOU symlink attack via loop device]
osv·2026-04-03·CVSS 4.7
CVE-2026-27456 [MEDIUM] CVE-2026-27456: [util-linux: mount(8) TOCTOU symlink attack via loop device]
[util-linux: mount(8) TOCTOU symlink attack via loop device]
No detection rules found.
No public exploits indexed.
Bugzilla
CVE-2026-27456 util-linux: TOCTOU in the mount program when setting up loop devices [fedora-all]
bugzilla·2026-04-06·CVSS 4.7
CVE-2026-27456 [MEDIUM] CVE-2026-27456 util-linux: TOCTOU in the mount program when setting up loop devices [fedora-all]
CVE-2026-27456 util-linux: TOCTOU in the mount program when setting up loop devices [fedora-all]
Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.
Bugzilla
CVE-2026-27456 util-linux: TOCTOU in the mount program when setting up loop devices
bugzilla·2026-04-03·CVSS 4.7
CVE-2026-27456 [MEDIUM] CVE-2026-27456 util-linux: TOCTOU in the mount program when setting up loop devices
CVE-2026-27456 util-linux: TOCTOU in the mount program when setting up loop devices
util-linux is a random collection of Linux utilities. Prior to version 2.41.4, a TOCTOU (Time-of-Check-Time-of-Use) vulnerability has been identified in the SUID binary /usr/bin/mount from util-linux. The mount binary, when setting up loop devices, validates the source file path with user privileges via fork() + setuid() + realpath(), but subsequently re-canonicalizes and opens it with root privileges (euid=0) without verifying that the path has not been replaced between both operations. Neither O_NOFOLLOW, nor inode comparison, nor post-open fstat() are employed. This allows a local unprivileged user to replace the source file with a symlink pointing to any root-owned file or device during the race window
Wiz
CVE-2026-27456 Impact, Exploitability, and Mitigation Steps | Wiz
blogs_wiz·CVSS 4.7
CVE-2026-27456 [MEDIUM] CVE-2026-27456 Impact, Exploitability, and Mitigation Steps | Wiz
## CVE-2026-27456 :
Linux Debian vulnerability analysis and mitigation
util-linux is a random collection of Linux utilities. Prior to version 2.41.4, a TOCTOU (Time-of-Check-Time-of-Use) vulnerability has been identified in the SUID binary /usr/bin/mount from util-linux. The mount binary, when setting up loop devices, validates the source file path with user privileges via fork() + setuid() + realpath(), but subsequently re-canonicalizes and opens it with root privileges (euid=0) without verifying that the path has not been replaced between both operations. Neither O_NOFOLLOW, nor inode comparison, nor post-open fstat() are employed. This allows a local unprivileged user to replace the source file with a symlink pointing to any root-owned file or device during the race window, causing th
https://github.com/util-linux/util-linux/commit/5e390467b26a3cf3fecc04e1a0d482dff3162fc4https://github.com/util-linux/util-linux/releases/tag/v2.41.4https://github.com/util-linux/util-linux/security/advisories/GHSA-qq4x-vfq4-9h9ghttps://github.com/util-linux/util-linux/security/advisories/GHSA-qq4x-vfq4-9h9g
2026-04-03
Published